Centralizer device for casings in boreholes



Dec. 5, 1967 DREYFUSS 3,356,147

CENTRALIZER DEVICE FOR CASINGS IN BOREHOLES Filed April 5, 1966 uvi I i ATTORNEY United States Patent ABSTRACT OF THE DISCLOSURE A field-assemblable casing centralizer consisting of a pair of collars and connecting leaf springs secured to the collars by means of U-shaped offsetsseated in recesses in the inner faces of the collars and secured by overlying tongues.

This invention relates to centralizer devices to be mounted on oil well casings for maintaining substantially uniform clearance between the casing and the bore wall both for protecting the casing in running into the well and preparatory to cementing.

Such centralizers conventionally have consisted of axially-spaced collars for reception about the casing and connected by bowed leaf springs, bars, or wires arranged annularly about the collars. The bowed springs or other elements frequently are constructed of high tempered spring steel to better resist the stresses and abrasion to which the centralizers are subjected in being run into the well on the casing. It has been found that the regions of attachment of the bowed elements to the collars frequently do not withstand these stresses and abrasions, especially where the bows are welded to the collars causing changes in the physical properties of the affected metal.

Centralizers with different diameters of collars and with bowed elements of different lengths, curvature, and shaping, for instance, helical twisting, are frequently neces sary in accordance with the diameter of the casing being run and of the bore hole, and the nature of the geological formations being penetrated. To keep down the expense of the well completion operations, as little time as possible should be lost in the preparation and mounting of the centralizers. Thus, it is necessary to keep in stock a large number of different types and sizes of centralizers ready for these different uses.

The present invention has for its object to provide a centralizer which may be readily assembled in different combinations and sizes of collars and bows.

Another object is to provide a centralizer which will better resist the stresses and abrasions incident to normal use in the well than previous centralizers.

These objects and others hereafter appearing are attained by the novel centralizer device hereinafter described which consists in general of a pair of collars, conveniently split and hinged and otherwise secured together, for em bracing the casing, and bowed leaf springs connecting the collars and secured at their ends thereto. The leaf spring and collar attachments are effected by means of an annular series of recesses or pockets preferably in the inner face of each collar in which recesses or pockets are snugly nested generally U-shaped offsets in the ends of the bowed elements. Tongues projecting circumferentially from the collar overlie the nested offsets and firmly maintain the assembly. The assembly operation, utilizing collars and bowed elements of the type and size desired, can be readily effected in the field or in a shop nearby. No welding is necessary, and the assembled collars and bowed elements are not maintained under bending or torsional stress nor are separate attaching elements required.

In the accompanying drawing which illustrates the invention,

FIG. 1 is an elevational perspective showing the novel centralizer mounted on a casing section;

FIG. 2 is a detail longitudinal (axial) section taken on line 22 of FIG. 1;

FIG. 3 is an end view of one of the collars disassembled from the bowed elements and casing; and

FIG. 4 is a partial inside view of one of the collars assembled with a bowed element.

FIG. 1 shows a portion of a conventional casing section 7 having any type of stop collar 8 secured thereto between the end collars, generally designated 9 and 10, of the novel centralizer device. Connecting the collars and secured at their ends thereto are bowed elements 11, preferably of spring steel straps, six being provided in this instance arranged symmetrically about the collars. At each end of each bowed element 11 there is provided a generally U-section outward offset, as at 12, for a purpose to be described.

The collars preferably are identical, although one of them may be otherwise formed. The novel collar, in this instance, is of the split type, with the halves connected by pinned hinges, as at 15 and 16. Annularly disposed about the collar, in accordance with the number of bowed elements to be used, are recesses or pockets, generally designated 17, conveniently formed by cutting out rectangular slots during the forming operation. Each recess has upper and lower shoulders 18 and 19 which are axially spaced apart sufiiciently to snugly but freely receive therebetween an offset element 12 at the end of one of the bowed elements 11. The parts 20 and 21 of the collar above and below each recess 17that is, the collar portions which, in the assembly, are traversed by portions 22 and 23 of a bowed element in the assemblyare recessed outwardly by the amount at least equal to the thickness of the bowed element portions 22 and 23 so that these latter portions, in the assembly, will be within the general corrfines of the inner surface of the collar, as represented by the face portions 24 between recesses 17. Projecting from the collar at one side of each recess 17 there is a tongue 25 which tongues, in the normal unassembled condition of the collar, as in FIG. 3, project circumferentially and inwardly so as to clear the recesses 17 for insertion and nesting therein of offsets 12 at the ends of bowed elements 11. In the assembly, these tongues are bent against the inner faces of offsets 12 so as to firmly secure the bowed elements to the collar. The sides edges 27 and 28 of recesses 17 are circumferentially spaced to freely receive the end of a bowed element 11 therebetween.

In operation, the centralizer will first be assembled of collars and bowed bars or leaf springs of the desired size and configuration. The end portion of each such bowed element will be inserted beneath a tongue 25 and nested in the corresponding collar recess 17. The recess 17, between its opposing axially-facing shoulders 18 and 19, as stated, will be positioned to freely but snugly receive the corresponding bowed element offset 12. Also, preferably, the inner faces of bowed element parts 22 and 23 will be flush with the inner face portions 24 of the collar in the assembly to form a generally smooth inner face for opposing the casing. The outer face portions of offsets 12, preferably, will be flush with the outer surfaces of portions 20 and 21 of the collar, as indicated in FIG. 2. To complete the assembly, tongues 25 will be bent, as shown in FIGS. 2 and 4, across and in engagement with the inner faces of ofisets 12. The bowed elements may be applied to the outer rather than the inner faces of the collars upon reversal of the offsets 12 and the collar indentations. Moreover, the tongues 12 may be secured at both ends to the collar and the bowed elements slipped endwise into recesses 17.

Thus, proper collars and bowed elements 11 can be withdrawn from a general stock of these parts of different shapes, kinds, and sizes and assembled readily either in the field or in a shop near the well being completed. The assembled bowed elements will be firmly held against both axial and circumferential displacement relative to the collars by the nesting offsets 12 and recesses 17. If desired, an additional shoulder may be provided in the bowed elements, as at 29. In applying to a casing section, the halves may be disconnected and then assembled about the casing and re-hinged at 15 and 16. Other means of assembly about a casing may be utilized if desired. During downward running of the casing, stop collar 8 will bear against lower centralizer collar 10 to move the centralizer downwardly into the well. In case it is desired to reciprocate the casing or to withdraw the casing from the bore, both such operations can be performed. It is particularly important that the attached collars and end portions of the bowed elements, while firmly secured together, are not under stress, and no welding is required such as might deleteriously affect the characteristics of the metal. While such centralizers, ordinarily, are cemented into the well, it would be possible, if necessary, to disassemble a centralizer by bending the tongues outwardly sufificiently to permit withdrawal of offsets 17 from the recesses 12.

The invention may be modified in various respects as will occur to those skilled in the art, and the exclusive use of all modifications as come within the scope of the .appended claims is contemplated.

I claim:

1. In a centralizer of the type having spaced, aligned collars and connecting bowed elements, collar and bowed element attaching means comprising a radial recess in a lateral face of the collar forming axially-spaced, opposing shoulders, a generally U-shaped offset in the end portion of said bowed element nested in said recess, and a tongue projecting from at least one side edge of said recess across said offset and confining said element in said recess.

2. Centralizer collar and bowed element attaching means as described in claim 1 in which said offset is snugly received and secured in said recess without bending or torsional stress.

3. Centralizer collar and bowed element attaching means as described in claim 1 in which said offset is freely but snugly received between said shoulders for resisting relative axial displacement of said collar and said bowed element.

4. Centralizer collar and bowed element attaching means as described in claim 1 in which said bowed element is formed from spring strap material.

5. Centralizer collar and bowed element attaching means as described in claim 1 in which said tongue is bendable without damaging said collar from a position clearing said recess, to permit insertion of said bowed element into said recess and withdrawal of said element therefrom, to its attaching position extending across said recess in engagement with said offset.

6. Ceneralizer collar and bowed element attaching means as described in claim 1 in which said recess is formed by a cut-out portion of said collar, said tongue projecting circumferentially from the body of the collar adjacent said portion.

7. Centralizer collar and bowed element attaching means as described in claim 1 in which the part of said. collar lateral face traversed by said bowed element in the assembly is radially recessed an amount at least substantially equal to the thickness of said bowed element adjacent said offset for accommodating said element within the general circumferential confines of said collar.

8. In a centralizer of the type having axially spaced collars for reception about a casing and outwardly bowed elements connecting said collars, bowed element and collar attaching means comprising an annular series of recesses in the inner face of at least one of said collars, generally U-shaped offsets in at least one end of each of said bowed elements, respectively snugly nested in said recesses, and tongues projecting circumferentially from said collar face across and engaging said offsets and within the general confines of said inner face for detachably securing together said collar and said elements.

References Cited UNITED STATES PATENTS 2,680,488 6/1954 Atkinson l66241 2,738,019 3/1956 Atkinson l66241 3,055,432 9/1962 Park 166--241 ERNEST R. PURSER, Primary Examiner.

DAVID H. BROWN, Examiner. 

1. IN A CENTRALIZER OF THE TYPE HAVING SPACED, ALIGNED COLLARS AND CONNECTING BOWED ELEMENTS, COLLAR AND BOWED ELEMENT ATTACHING MEANS COMPRISING A RADIAL RECESS IN A LATERAL FACE OF THE COLLAR FORMING AXIALLY-SPACED, OPPOSING SHOULDERS, A GENERALLY U-SHAPED OFFSET IN THE END PORTION OF SAID BOWED ELEMENT NESTED IN SAID RECESS, AND A TONGUE PROJECTING FROM AT LEAST ONE SIDE EDGE OF SAID RECESS ACROSS SAID OFFSET AND CONFINING SAID ELEMENT IN SAID RECESS. 